In a World of exploding "social networking" websites here's one that I thought was rather interesting. Basically you put a small software agent on your workstation and it keeps track (no its not spyware) if there are any updates to that software available.
More that that the agent keeps track of what software you use and how long you use it for. It then stores that information in an online profile. That profile can then be viewed by others so see what software you are using. This can alert people the fact that you've found a new piece of software and you are using it extensively.
Finally, all the program usage statistics are cumulated by application so you can exactly how much programs like Firefox and IE are being used.
Interesting concept isn't it?